Currently, neither configurer nor Maker is aware of the standard zig
package path, and the root path is stored as a bare string rather than
relative to a known base directory. Without changing that, we must
construct a cwd relative path here rather than using knowledge of the
standard package path plus package hash.
Also fixes a bug that would have been prevented by implementing the
accepted proposal https://github.com/ziglang/zig/issues/25315
Number of generated files is recorded in serialized Configuration. Maker
preallocates array of generated files so that loads and stores can be
synchronization-free (protected by the dependency tree ordering).
More progress on Compile Step Zig CLI lowering.
Andrew Kelley